Highly efficient liquefaction of wheat straw for the production of bio-polyols and bio-based polyurethane foams

Abstract

Highly efficient liquefaction of wheat straw (WS) was achieved using alcohol/water mixed solvent at low temperatures under medium pressure in the presence of an alkaline catalyst. Effects of liquefaction conditions, e.g., temperature, residence time, catalyst, and type of solvents on the yields of bio-polyols (BP) and solid residue were investigated. Liquefaction of WS in ethanol/water (50/50, v/v) using NaOH (15wt.% w.r.t. WS weight) at 270°C for 120min produced 72.1% yield and the BP has a weight-average molecular weight of 1000g/mol and hydroxyl number of 449mgKOH/g. The obtained BP was successfully utilized to substitute up to 50wt.% of PPG400 for the preparation of bio-based PU (BPU) foams using a low amount of foaming catalyst (0.5wt.%). The BPU foams exhibit good thermal conductivity (0.040–0.050W/(mK)) and thermal stability comparable to those of a reference foam prepared with 100% PPG400.